June 6, 1895] 



NA TURE 



135 



al)out 2000 figures, illustrating ever)' known genus of diatoms, 

 anil every species found in the North Sea and countries txirdering 

 it, including Great Britain. 



The second edition of " Elements of Marine Surveying," by 

 lite Rev. J. L. Robinson, lately published by Messrs. Macniillan 

 and Co., contains several very useful additions and improve- 

 ments. Young marine surveyors will find the volume an 

 excellent aid to the study of the theoretical side of their pro- 

 fession, and would do well to inchide it in their outfit. 



Particulars of editions of Gilbert WHiite's " Natural 

 History and Antiquities of Selborne '' have been compiled by Mr. 

 Edward A. Martin, for the Selborne Society. Since the original 

 edition was published in 1789, twenty-three other editions have 

 appeared. The list compiled by Mr. Martin, gives the dates of 

 the various editions, publishers, printers, editors, numlier of 

 pages, and general descri]5tii>n. 



The annual report of the Royal Botanic (hardens, Trinidad, 

 for the year 1894, compiled by the Superintendent, Mr. J. H. 

 Hart, furnishes evidence of the practical value of these colonial 

 Ixitanic gardens, and of their relation with the central institution 

 at Kew. Under the Economic Section, information is given of 

 the growth in the island of the sugar-cane, cacao, coffee, yam, 

 gambler, vanilla, the Brazil nut, and cola, and of the principal 

 enemies of these crops, and the best mode of combating them. 



We have received Part i. of "The P^lowering Plants and 

 Ferns of New South Wales," with especial reference to their 

 economic value, by Mr. J- H. Maiden, assisted by Mr. W. S. 

 Campbell, and issued under the authority of the Department of 

 Mines and -Vgriculture for New South Wales. The present 

 part contains descriptions and coloured drawings of four species — 

 Tihpea speciosissima. Eucalyptus (orymbosa, Actiiiatus heliaiithi^ 

 M\'i Ai'acia glaucescens. It is intended in this way to illustrate 

 the principal flowering plants and ferns of the colony. 



The additions to the Zoological Society's Gardens during the 

 past week include a Panolia Deer (Cervus eldi, i ) from Hainan, 

 presented by Mr. Julius Neumann ; a Ruddy Ichneumon ; 

 {JIt'rpt'stes smithii) from India, presented by the Earl of 

 Hojietoun ; a Spotted Ichneumon (Herpisles tu'palnisis) from 

 India, ]>resented by Mrs. Thompson ; a Rosy-faced Love-Bird 

 (Agapomis pullaria from West Africa, presented by Mr. Cecil 

 M. Bevan ; a Rufescent Snake (Leptodira rufisicns) from South 

 Africa, presented by Mr. J. E. Matcham ; a Spiny Tree 

 I'lircupine (Sphingurus spiiiosus) from Peru, a Blossom-headed 

 I'arrakeet (Faltconiis cyaiiocephala] from India, two Tuberculated 

 Iguanas (Iguana tuherculata) from South America, deposited ; 

 two Guira Cuckoos (C«j>a/zV7'ro-«a) from Para, purchased :a 

 Ia|\inese Deer (Cen'us sika, 9 ), born in the Gardens. 



OUR ASTRONOMICAL COLUMN. 



The Motion ok the Solar System. — The methods 

 elaliorated by .Argelander and .\iry for the numerical solution of 

 this jiroblem have been followed with more or less variation by 

 a host of investigators. -Vsa rule the deviations in method have 

 involved matters of detail rather than any fresh departure. 

 \ arious suppositions have been made as to the motions of the 

 stars themselves (iitotus peculiarcs) : that the magnitude and 

 direction of these motions have no connection with position, or 

 that, in general, all these motions takeplacewith the same angular 

 velocity parallel to the galactic circle. Stars may be grouped 

 according to their brilliancy, or the amount of their ]iroper 

 motion, or they may be arranged with more or less ingemiity 

 according to their apjiarcnt position ; but when the linal equa- 

 tions are .solved, the results are found to be fairly accordant. 

 This fact has been recently demonstrated liy M. Pannekoek, 

 who, to vary the problem as much as possible, has based his 

 investigations on the type of spectnnn presented by the star. 



NO. 1336, VOL. 52] 



The zone from which the stars are selected is somewhat limited, 

 being restricted to 0° — 20° of declination, the spectra of which 

 have been observed at Potsdam. The stars have been divided 

 into four groups, according to the amount of the proper motion, 

 with the following results : — 



Stars of the First Type. 



The result derived from stars of small proper motion 

 of either the first or second type of spectra is scarcely 

 accordant with previous investigations. The Right Ascension 

 of the one and the Declination of the other are sensibly 

 different from results involving larger numbers of stars. The 

 author remarks, however, that all the values in R.A. can 

 be rendered less discordant by an increase in the constant of 

 precession of -l-o"-oi, and in Declination by assuming a constant 

 negative error in the proper motions' themselves. Here we have 

 again evidence that no rearrangement of groups materially alters 

 the position assigned for the apex of the sun's way ; but when 

 processes sensibly difterent in their conception are employed, 

 the accordance in the results is not so gratifying. For instance, 

 the attempt to determine the position of the apex from ^'oge^s 

 measurements of the motion of stars in the line of sight led to 

 either of the two results, according to the method of " weighting" 

 employed. 



I. II. 



a . 2"o6i + l°2-o . 159-7 + 20-2 



8 • + 45-9± 9-2 • + 50-0+ 14-3 



Here, if the Declination be fairly satisfactor)-, the Right 

 Ascension is hopelessly discordant. On the other hand. Dr. 

 Kobold's treatment of the problem according to the graphical 

 method suggested by Bessel, a method which does not easily 

 lend itself to numerical treatment, gives a fairly satisfactory- 

 result in R.A., but the Declination will scarcely be accepted. 

 The position assigned to the apex by this method is a = 266^-5 r 

 5 — 3°-I. This result is based on 1425 stars, and ought to be 

 entitled to considerable weight if it could be .satisfactorily 

 demonstrated that all ambiguity, which arises from the definition 

 of the poles of the great circles in which the proper motions take 

 place, had been satisfactorily removed. This question is still 

 suh judiee, and while distinct methods give conflicting results, it 

 is not wise to insist too strictly on the direction of the motion of 

 the solar system. 



The Rotation of M.vrs. — Among numerous obser\ations ot 

 the planet Mars during the last opposition, Mr. Percival Lowell 

 gave his attention to the measurement of the longitudes of some 

 of the more conspicuous markings. The observations covered 

 36 points in all, and were made with a power of 440 on the 

 l8-inch refractor of the Lowell Observator)'. The fir.st fact that 

 emerged from the observations was that all the longitudes as 

 given in Marth's ephemeris were affected by a systematic error 

 of about 5 : or, in other words, the Martian features were 

 retarded by abi>ut twenty minutes as compared with the com- 

 puted times. The cause suggested for the discrepancy between 

 the calculated and observed positions is that the received time of 

 rotation of the planet is a trifle too small, and that the longitudes 

 are consequently falling slowly behind their predicted times of 

 meridian passage. 



.A soinewhat similar discrepancy appears to have been noted 

 by Prof Keeler in 1892, who ascribed it partially to the constant 

 error in estimating the position of the diameter of a large disc 

 (Astrophysical fouriial. May). 



The Sun's Stellar .Mac.niti de. — .\ new method of com- 

 puting this important constant, being the number representing the 

 sun's brightness on the scale in w hich the magnitudes of stars are 

 represented, has been employed by Mr. Gore (Knowledge, Jtine). 

 Taking one of the outer planets, the known size and distance 



